The present invention relates generally to radio communication systems. More particularly, the present invention relates to a method and associated apparatus for distributed dynamic paging area clustering under heterogeneous access networks.
As wireless technology and the Internet are commercially developed, mobile Internet access becomes more and more popular globally. In the developing third generation and fourth generation (3G and 4G, respectively) wireless system, wireless and Internet technology will be combined together. In such systems, a mobile host is free to move about a region while remaining in radio contact with a base station or other fixed infrastructure access point. Each base station of a network serves mobile hosts in a geographic area surrounding the base station. As the mobile host moves, communication with the mobile host is handed off from one base station to another. Research and standardization efforts are currently underway with a goal to integrate both cellular technologies and Internet technologies. Paging technology is one such technology.
Paging technology partitions all cells in a cellular system into several different areas called paging areas. A mobile host travelling across these paging areas is required to register a new location whenever it moves from one paging area to a different one. When the mobile host is within a paging area, its exact location is unknown to the system. As a result, when a call arrives, the exact location of the called MH is determined by sending paging message to all cells of the MH's paging area. Paging technology has proven to be very effective to reduce the power consumption at the mobile host.
Paging technology is used to track a mobile host (MH) that is in a dormant mode. The mobile host enters the dormant mode when not actively communicating in order to conserve battery power. While in the dormant mode, however, a MH is capable of receiving a signal from a nearby access point, reporting to it an area identifier (ID) indicating the paging area where the MH is traveling. The paging area is the portion of a network or system to which a paging signal intended for a particular MH is broadcast. While traveling from one paging area to another, the MH can recognize if and when it crosses the boundary between paging areas and enters another paging area because it begins receiving a different area ID signal upon crossing the boundary. The MH, upon reception of the different area ID signal, wakes up from the dormant mode to an active mode and sends a signal to register itself with the new paging area.
In 3G and 4G wireless systems, the backbone is assumed to be an Internet Protocol (IP) network. IP is a standardized communication format applicable to both wireless and wireline communication systems, or a combination of the two. An IP based paging protocol is necessary for 3G and 4G wireless systems.
A challenge in the development of IP paging technology is how to assign paging areas. Two issues have been identified with defining and arranging or configuring paging areas. The first issue is on the size of a paging area. If each paging area is sized to be relatively large, significant network resources must be diverted to paging operations conducted in that area. A paging signal must be broadcast extensively to cover the large area to locate just one MH. If each paging area is defined to be relatively small, a significant amount of energy will be used in the MH for responding to paging signals. If paging areas are defined to be relatively small, the MH will frequently cross a boundary between two adjacent paging areas. Each time the MH crosses a boundary, it has to wake up and register with a new area, dissipating battery power.
The other issue in sizing paging areas is overlapping of paging areas. In current communications systems, each paging area is allowed to have a limited number of area IDs (usually one area ID). Some arrangements are needed to dynamically define and arrange paging areas under this constraint on the number of area IDs that each paging area is allowed to have.
Much existing research has been done on how to construct an appropriate paging area. In one reference, it is proposed to use an individual location area concept that treats mobile user with different mobility and call characteristics differently to reduce the average signaling cost of mobility management. Based on this concept, several approaches such as a time-based strategy and profile-based strategy have been introduced for the cellular paging systems. However, all this research has been directed to design a static paging area which means the paging area construction will be fixed all the time. However, simulation results show that such fixed paging area design will lead to a high paging cost under many circumstances. This is because the user traffic varies from time to time; a static paging area may not be able to cover the traffic pattern well so that the location update cost increases significantly.
Current paging technology uses fixed paging areas. Paging areas are manually defined and arranged, and once defined and arranged, they are seldom changed. These manually defined paging areas are thus inflexible and cannot adapt themselves to changes in communication traffic. Also, since paging areas are defined manually, human errors are unavoidable. Some proposals have been made on dynamic configuration of paging areas, but these proposals permit unlimited overlapping of area IDs. In these proposals, each MH dynamically computes and shapes its optimal paging area size according to the traffic and movements. Naturally, each paging area overlaps in those individual paging schemes.
Much research has been done to optimize paging area configuration so that the overall paging cost can be minimized. The total paging cost for the system comes from two parts, location update cost and paging cost. The location update cost is the resource used to update the user location when the user moves into a new paging area. The paging cost is the resource used to send messages to the user within each paging area. A properly designed paging area should be able to minimize the overall paging cost.
A dynamic paging area construction algorithm has been proposed. For example, a dynamic method for configuring sizes and shapes of paging areas, along with an individual location, has been proposed. However, it is difficult to control location area overlap in the proposed method. Paging area overlap has to be controlled in most cellular system such as the Personal Digital Cellular (PDC) system in Japan, the Global System for Mobile communication (GSM) and wideband code division multiple access (W-CDMA) systems. These wireless systems are designed to broadcast a restricted number of paging area IDs per base station at a time. As a result, a base station can not belong to many location areas simultaneously.
Accordingly, there is a need for an improved paging area construction method and apparatus.